In hemorrhagic shock experiments on cats, it has been shown that following transfusion of shed blood (after a certain period of decreased blood pressure), skeletal muscle ATP and creatine phosphate levels (CP) returned towards the initial control values whereas fat tissue levels remained low indicating severe irreversible damage at a cellular level. Closely related to these results was the finding according to which there was no significant change in the skeletal muscle water content throughout the post-transfusion phase. On the other hand, the fat tissue water content increased simultaneously with the increase in hematocrit. In line with our planned comprehensive hemodynamic studies and to help introduction of some of the techniques to clinical setting, an effort was made to simplify the thermodilution technique for measuring cardiac output. The simplified procedure permits rapid evaluation and a very simple electronic processing system can be used.